Isotope tracer studies on the carbon dioxide exchange in pregnant primates

The exchange of carbon dioxide in the pregnant rhesus monkey has been studied quantitatively using sodium bicarbonate-(14)C and applying the model of a system of seven compartments. The transfer rates among the various compartments, compartment sizes, and the rate of production of carbon dioxide by fetus and mother were determined with a computer programmed to fit the theoretical model to the data by adjusting the parameter values of the model until a "best fit" was obtained. It was confirmed that the exchange of carbon dioxide between fetal and maternal blood across the placenta is rapid, that between fetal blood and amniotic fluid is slow, and that there is no appreciable exchange between maternal blood and amniotic fluid. The mean net production of CO(2) by fetus was 0.476 +/-0.0402 mmoles/kg.min, and that by mother was 0.373 +/-0.0279 mmoles/kg.min.

This study was designed to explore relationships among maternal and fetal amino acid blood concentrations and amniotic fluid amino acid levels in pregnant rhesus monkeys. Although there was no constant pattern for all amino acids in the three body fluids, we observed specific patterns for most neutral amino acids, imino acids, and acidic amino acids relative to their concentrations in maternal blood, fetal blood, and amniotic fluid. Moreover, there was no correlation between fetal phenylalanine blood levels and phenylalanine concentrations in amniotic fluid indicating that amniotic fluid phenylalanine levels would not be useful to monitor fetal phenylalanine blood concentrations during pregnancy.

Comparison of the concentrations of polychlorinated dibenzo- p-dioxins, dibenzofurans, and dioxin-like polychlorinated biphenyls in maternal and fetal blood, amniotic and allantoic fluids in cattle

Vertical transmission from mother to infant is the primary mode for the spread of human immunodeficiency virus type 1 (HIV-1) in the pediatric population. AZT, the nucleoside analogue, is offered to most HIV-1-positive pregnant women in the United States and is currently the only drug approved to prevent viral transmission (Mofenson, ’98). A highly successful approach to lowering the HIV-1 transmission rate by threeto fourfold in clinical trials includes a combination of oral AZT starting at 14 weeks of pregnancy, infusion of drug during labor and delivery, and oral administration of AZT to the newborn during the first 6 weeks of life (Sperling et al., ’96). Only 5% of the infants born to the approximately 7,000 HIV1-positive women who become pregnant yearly in the United States are HIV-1 positive, in part, because most are given AZT therapy. Therefore, most AZT-exposed children are uninfected and are likely to have a normal life span, with time for the appearance of any potential long-term consequences of the transplacental AZT exposure. AZT is weakly carcinogenic in adult mice exposed orally for a lifetime (Ayers et al., ’96), but AZT is a moderately strong dose-dependent carcinogen in mice exposed in utero or as neonates during the first 2 weeks of life (Ayers et al., ’97). Given at tumorigenic doses transplacentally, AZT has been shown to be incorporated into organ DNA of newborn mice. In addition, newborn monkeys administered AZT at doses 20% of the human daily dose for the second half of gestation have exhibited incorporation of AZT into tissue DNA (Olivero et al., ’97). AZT-induced DNA damage may be directly mutagenic in that in transplacentally-exposed mice, AZT-DNA incorporation is associated with H-ras mutations in topically promoted skin tumors appearing after 1 year of age (Zhang et al., ’98). Near-term pregnant rhesus (Macaca mulatta) monkeys were dosed by infusion with an amount of AZT similar to the daily dose received by pregnant women in order to study the genotoxicity of transplacental AZT exposure in an animal model relevant to the human. This study design also allowed for exploration of the relationship between AZT pharmacokinetics and AZT incorporation into DNA (Poirier et al., ’99). In the case of four of the maternal-fetal pairs for which extensive AZT pharmacokinetic parameters have been previously published (Patterson et al., ’97), AZT was administered continuously by infusion for 4 hr up to delivery. A separate, previously unreported, rhesus dam was given AZT by infusion for 3 hr, followed by a 1-hr drug-free interval before delivery. AZT and AZTG concentrations in maternal and fetal blood, amniotic fluid, and fetal organs were compared with AZT-DNA incorporation levels in fetal organs for this maternal-fetal pair. For the 4 hr before hysterotomy, four term pregnant monkeys were continuously infused with 8 mg AZT/kg body weight. This short-term exposure resulted in AZT incorporation into DNA of fetal liver, lung, heart, skeletal muscle, brain, testis, and placenta, which varied between 29 and 1,944 molecules of AZT/10 nucleotides. As determined by total radioactivity, AZT and combined metabolites varied between 0.94 and 5.20 mg AZT equivalents/g tissue. The fifth animal was infused with 17.3 mg AZT/kg body weight for approximately 3 hr, followed by 1 hr without drug before hysterotomy. Variable levels of AZT (16–147 molecules of AZT/10 nucleotides) were incorporated into organ DNA of this preparation, similar to the other four monkeys, while the organ tissues contained less variable concentrations of AZT and metabolites (0.86–2.05 mg AZT equivalents/gm tissue). One hr after discontinuation of drug, concentrations of AZT and the 39-azido-39-deoxythymidine-b-D-glucuronide (AZTG) in fetal blood and amniotic fluid were twoand threefold higher than those in maternal blood in the case of the single animal at hysterotomy. Most AZT pharmacokinetic parameters in the fifth monkey were similar to those previously reported for the first four monkeys (Patterson et al., ’97) and to those observed in a similar study of pregnant women (O’Sullivan et al., ’93). The data indicate that in pregnant rhesus monkeys, a 3–4-hr infusion of AZT results in incorporation of this HIV therapeutic into the DNA of placenta and most fetal organs. Because the known pharmacokinetics of AZT are similar in the monkey and human, the data imply that even after short-term AZT infusion to the mother just before delivery, the human fetus may also be subject to incorporation of AZT into DNA.

Disposition of ethanol in maternal blood, fetal blood, and amniotic fluid of third-trimester pregnant ewes

Background: Intrapartum assessment of the fetus is a challenging task. And a good fetal surveillance during labour often entails monitoring the fetal heart rate with cardiotocography (CTG). The fetal heart rate pattern is an indicator of medullary response of fetal brain to the acidemia, blood volume changes and hypoxemia, as the brain modulates the fetal heart rate. But specificity of CTG is low that’s why generally intrapartum cardiotocography is combined with a second variable, such as Fetal Scalp Blood sampling, to improve its specificity. The increased intervention rates associated with non-reactive cardiotocography can be reduced with the use of fetal scalp blood sampling. Objectives: To compare frequency of caesarean section with use of non- reactive Cardiotocography versus non-reactive Cardiotocography and fetal scalp blood sampling. To determine the immediate neonatal outcome in terms of death, Apgar score and need for intensive care unit admission after delivery. Study Design: This study was cross sectional analytical study. Settings: Obstetrics and Gynaecology department, Unit-I, Lady Willingdon Hospital, Lahore, affiliated with King Edward Medical University. Duration: The duration of study was 1 year. Methodology: The non-probablity purposive sampling technique was used in this study. 100 patients in labour at term presented to labour room of Lady Willingdon Hospital, and fulfilling the inclusion criteria were enrolled in this study. After taking informed written consent, the patients were divided into two groups (A and B). In group A, 50 cases having non-reactive Cardiotocography were taken and according to fetal assessment by Cardiotocography all were taken for caesarean section. In group B, 50 cases having non-reactive Cardiotocography were taken and fetal assessment was done by continuous Cardiotocography as well as fetal scalp blood sampling. In group B, fetal hypoxia was assessed by fetal blood pH. Only those cases in group B underwent caesarean section, where fetal hypoxia was confirmed by fetal blood pH (pH=<7.20). Apgar score at 1 min and 5 min and admission to neonatal intensive care unit (NICU) was noted for postnatal fetal assessment in both the groups. Data was entered and analyzed through SPSS version 21. To calculate sensitivity, specificity, Positive predictive value (PPV), negative predictive value (NPV) and fetal scalp blood pH 2x2 tables were generated, taking pH as gold standard. Results: In this study among 100 patients, the mean age of the patients was noted as 27.64±4.38 years and the mean gestational age was noted as 39.30±1.05 weeks. The mean Apgar score at 1 minute of the baby was noted as 5.62±1.39, whereas at 5 minutes was noted as 6.76±2.09. In group B among 50 cases the mean pH value of fetal scalp blood was noted as 7.25±0.048. Fetal scalp blood sampling was normal in 20/50 (40%) patients, borderline in 24/50 (48%) patients, whereas it was abnormal in 6/50 (12%) patients. In group A, among 50 cases all underwent lower segment Caesarean section (LSCS). In group B, among 50 cases, 30/50 (60%) cases underwent LSCS while 20/50 (40%) underwent spontaneous vaginal delivery. In group A, 28/50 (56%) cases had Apgar <7 at 5 minutes while in group B, 18/50 (36%) cases had Apgar <7 at 5 minutes. In group A, 4/50 (8%) cases died while in group B, no mortality was observed. There was significant difference observed between group A and cases in group B for all these factors. In group A, 10/50 (20%) cases had NICU admission while in group B, only 6/50(12%) cases had NICU admission. There was no significant difference observed between two groups in NICU admission. Conclusion: It was concluded that CTG coupled with fetal blood sampling for fetal pH versus carditocography alone is an accurate method for assessment of fetal condition in labour to decide the mode of delivery and neonatal outcome after birth.

SummaryTransfer of Ca from mother to fetus concurrent with transfer from fetus to mother was studied in 3 pregnant rhesus monkeys. Ca45 was injected into a fetal inter-placental vessel simultaneously with intravenous injection of Ca47 into the anesthetized mother. Samples of maternal blood (MB), fetal blood (FB), and amniotic fluid (AF) were assayed for Ca45, Ca47 and non-radioactive Ca. Initial loss of Ca47 from MB was matched by rapid initial appearance in FB (t 1/2 ≤ 6 min) and somewhat slower entry into AF. Similarly, Ca45 appeared in MB at a rate almost equal to the initial rate of loss from FB. The quantity of Ca crossing the placenta daily was at least 6–10 times that required for fetal skeletal growth.

To test the hypothesis that unconjugated bilirubin is equally distributed over the albumin molecules present in fetal blood and amniotic fluid in Rhesus (Rh) immunization. Molar concentrations of unconjugated bilirubin and albumin were measured in fetal blood and amniotic fluid samples, obtained before the first intrauterine transfusion in 30 nonhydropic, anti-D-alloimmunized fetuses, with gestational ages ranging from 20 to 35 weeks. Bilirubin concentration in amniotic fluid was best predicted by a combination of bilirubin concentration in fetal blood (P<.001), albumin concentration in fetal blood (P=.008), and albumin concentration in amniotic fluid (P<.001) (adjusted R2=0.91). The bilirubin/albumin ratios in fetal blood were linearly correlated with the bilirubin/albumin ratios in amniotic fluid (R2=0.75, P<.001). However, the bilirubin/albumin ratios in fetal blood were always higher than the bilirubin/albumin ratios in amniotic fluid (regression coefficient 1.4, 95% confidence interval 1.1-1.7). In our population, a bilirubin/albumin ratio in amniotic fluid of 0.10 or greater had a better sensitivity and specificity to predict severe anemia (Z hemoglobin -5 standard deviations or less) than the Queenan 4 or the Liley 2c line. The relation between fetal hemolysis and amniotic fluid bilirubin concentration is based on the linear correlation between bilirubin/albumin ratios in fetal blood and in amniotic fluid. The slope in Queenan's and Liley's chart follows that of the albumin concentration in amniotic fluid during gestation. III.

The pattern of ethanol and acetaldehyde appearance in blood after an oral ethanol gavage (4 g/kg body wt) was not different at 12 or 21 days' gestation compared to virgin rats. Five min after maternal ethanol administration, concentrations of ethanol in fetal blood were lower than in maternal blood; however, at 15 min after ethanol administration, fetal and maternal blood levels were similar. Ethanol concentrations in fetal blood and amniotic fluid were already at equilibrium 5 min after ethanol administration. Acetaldehyde concentrations in fetal blood and in amniotic fluid were undetectable at all the times investigated, with the exception of fetuses from two pregnant rats studied 3 h after ethanol administration. Alcohol dehydrogenase activity in fetal liver and in placenta at late pregnancy was very low or undetectable, suggesting a very low rate of ethanol oxidation in vivo. After intravenous administration of acetaldehyde (10 mg/kg body wt), blood acetaldehyde concentrations were higher in pregnant than in virgin rats. Acetaldehyde concentrations in fetal blood and in amniotic fluid were similar to maternal blood at 2, 5, and 30 min after injection. When circulating concentrations of maternal and fetal acetaldehyde, obtained after either ethanol or acetaldehyde administration, were plotted, it was found that fetal blood concentrations of acetaldehyde were only detectable when maternal blood concentrations were greater than 80 microM. Concerning the acetaldehyde oxidation capacity, both the high and low affinity components of aldehyde dehydrogenase activity in fetal liver and placenta were very low as compared with maternal liver. However, aldehyde dehydrogenase activity in fetal liver was much higher than in placenta.(ABSTRACT TRUNCATED AT 250 WORDS)

To investigate maternal and fetal folate and vitamin B12 concentrations in pregnancies affected by neural tube defects (NTD). Measurement of folate and vitamin B12 concentrations in amniotic fluid, fetal blood and maternal blood samples in midgestation. 32 women undergoing termination of pregnancy at 14-21 weeks gestation for social reasons (n = 24) or for fetuses with neural tube defects (n = 8). Fetoscopy before intra-amniotic injection of prostaglandins. In normal pregnancies there was a positive correlation between maternal and fetal serum folate, and the fetal serum and red blood cell folate concentrations were higher than the maternal. There were no differences in amniotic fluid, maternal blood or fetal blood folate concentrations between pregnancies with NTD and normal pregnancies. Although amniotic fluid vitamin B12 was lower in pregnancies with NTD, maternal serum vitamin B12 concentration was not reduced. In this small group of pregnancies with NTD at mid-gestation there is no evidence to suggest folate or vitamin B12 deficiency.

Does amniotic fluid analysis reflect acid-base balance in fetal blood?

BackgroundMyocardial dysfunction occurs in a variety of fetal disorders. Findings from adult cardiology, where n-terminal pro-B-type natriuretic peptide (nt-proBNP) is an established biomarker of left ventricular dysfunction have been extended to fetal life. Since fetal blood sampling is technically challenging we investigated amniotic fluid nt-proBNP for its suitability to diagnose fetal myocardial dysfunction.MethodsUltrasound, Doppler examination and echocardiography was applied to classify cases and controls. Amniotic fluid nt-proBNP to amniotic fluid total protein ratio was calculated and compared to the gestational age-dependent reference intervals. In a subset of cases, fetal and maternal plasma nt-proBNP levels were determined.ResultsSpecimen from 391 fetuses could be analyzed (171 cases, 220 controls). There was a high correlation between amniotic fluid and fetal blood nt-proBNP levels (r = 0.441 for cases; r = 0.515 for controls), whereas no correlation could be detected between maternal and fetal (blood and amniotic fluid) nt-proBNP concentrations. Specificity and positive likelihood ratio of amniotic fluid nt-proBNP to amniotic fluid total protein ratio were high (0.97 and 4.3, respectively).ConclusionAmniotic fluid nt-proBNP measurement allows diagnostic confirmation of fetal myocardial dysfunction. It may serve as a useful adjunct in addition and correlation to existing tests of myocardial function, particularly in the context of invasive fetal therapy, where access to the amniotic cavity is part of the procedure.

Detection of fetal blood contamination by amniotic fluid obtained during cordocentesis

The simultaneous transport of radiostrontium from mother to fetus and from fetus to mother was studied in two pregnant rhesus monkeys at term. Carrier- free Sr/sup 85/ was injected into the circulation of the intrauterine fetus simultaneously with the injection of carrier free Sr/sup 90/ into the maternal circulation. Serial samples of fetal and maternal blood as well as amniotic fluid were obtained and assayed for a period of 70 minutes post injection. One fetus and mother was sacrificed and various tissues as well as the carcasses were assayed for total Sr/sup 90/ and Sr/sup 90. content. The disappearance of radiostrontium from the circulatory system into which it was injected was rapid and could be described by a power function of time during the period 10 to 70 minutes. The maximum concentration of radioisotope appeared in the contiguous circulation at 10 to 20 minutes after injection. Although the data did not permit quantitative compartmental analysis and description of transfer rates, it was demonstrated that strontium rapidly traversed the placenta passing from fetal blood to maternal blood, as well as in the reverse direction. Strontium which entered either the fetal or maternal blood via placental transfer was deposited in a mannermore » equivalent to strontium injected directly into the blood. Fetal bone had a greater avidity for Sr per unit weight than did maternal bone but the larger mass of soft tissue and bone in the maternal organism resulted in the' fixation's of much more radioactivity in the mother than in the fetus. Both isotopes rapidly entered the araniotic fluid. The isotope from the fetal circulation appeared faster, reached a higher concentration, and attained equilibrium sooner than that from the maternal circulation. Observations of differences in tissue distribution and disappearance rates from the circulatory system were interpreted without invoking a specific dynamic mechanism for directional discrimination by the primate placenta. (auth)« less

In the United States, the nucleoside analogue drug 3'-azido-3'deoxythymidine (AZT; also called zidovudine or ZDV) is given to most pregnant women who produce a positive test result for HIV-1. To investigate transplacental distribution and genotoxicity of AZT, near-term pregnant rhesus (Macaca mulatta) monkeys and their fetuses were studied. Four pregnant monkeys were continuously infused with 8 mg AZT/kg body weight for the 4 hours just prior to hysterotomy at term. This short-term AZT exposure resulted in AZT incorporation into DNA of fetal liver, lung, heart, skeletal muscle, brain, testis, and placenta, which varied between 29 and 1944 molecules of AZT/10(6) nucleotides. In contrast, values for AZT and combined metabolites, determined by radioactivity, varied between 0.94 and 5.20 microg AZT equivalents/g tissue. A fifth animal, (H076), was infused with 17.3 mg AZT/kg body weight for approximately 3 hours, followed by 1 hour without drug before hysterotomy. Similar to the 4 other monkeys, variable levels of AZT (16-147 molecules of AZT/10(6) nucleotides) were incorporated into organ DNA of H076, whereas organ tissues contained less-variable levels of AZT and metabolites (0.86-2.05 microg AZT equivalents/g tissue). For H076, at hysterotomy 1 hour after discontinuation of drug, values for AZT and the 3'-azido-3'-deoxythymidine-beta-D-glucuronide (AZTG) in fetal blood and amniotic fluid were twofold and threefold higher than those in maternal blood. Most AZT pharmacokinetic parameters in the fifth monkey were similar to those previously reported for the first 4 monkeys and those observed in a similar study of pregnant women. These data show that a short-term AZT infusion in pregnant rhesus monkeys, which have similar AZT pharmacokinetics to those present in a pregnant human, results in incorporation of drug into the DNA of placenta and most fetal organs. Data imply that the human fetus may also be subject to incorporation of AZT into DNA even after short-term AZT infusion to the mother just before delivery.